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Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
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Transferable amikacin resistance in gram-negative bacterial isolates

J Kallová1, T Macicková, A Majtánová

  • 1Department of Microbiology and Virology, Comenius University, Bratislava, Slovakia.

Chemotherapy
|May 1, 1995
PubMed

Insights

New aminoglycoside resistance mechanisms involving AAC(6')-I enzymes were identified in Enterobacteriaceae strains from Europe. This transferable resistance, previously found in staphylococci, poses a significant public health threat.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Enterobacteriaceae are common human pathogens.
  • Aminoglycoside antibiotics are crucial for treating bacterial infections.
  • Emergence of antibiotic resistance in Enterobacteriaceae is a growing concern.

Purpose of the Study:

  • To investigate the mechanisms of amikacin resistance in Enterobacteriaceae.
  • To identify novel aminoglycoside resistance genes in clinical isolates.
  • To determine the transferability of aminoglycoside resistance.

Main Methods:

  • Isolation and characterization of amikacin-resistant Enterobacteriaceae strains.
  • In vitro susceptibility testing against various aminoglycosides.
  • Phosphocellulose paper binding assays to detect aminoglycoside-modifying enzymes.
  • Plasmid analysis and conjugation experiments to assess resistance transfer.

Main Results:

  • Seven Enterobacteriaceae strains exhibited resistance to multiple aminoglycosides, including amikacin, gentamicin, and tobramycin.
  • Resistance was attributed to the aminoglycoside acetyltransferase AAC(6 extprime)-I enzyme, a mechanism previously identified only in staphylococci and streptococci.
  • This AAC(6 extprime)-I mechanism was also found in two Klebsiella pneumoniae isolates.
  • Additional enzymes, AAC(3)-II and APH(2 extprime extprime), were detected in some strains.
  • Aminoglycoside resistance was transferable via plasmids ranging from 36-45 MD.

Conclusions:

  • The study identified a novel aminoglycoside resistance mechanism (AAC(6 extprime)-I) in Enterobacteriaceae, previously unrecognized in this bacterial group.
  • The presence of transferable R plasmids encoding these resistance enzymes highlights the potential for rapid dissemination of antibiotic resistance.
  • These findings underscore the need for continuous surveillance of antibiotic resistance mechanisms in clinical settings.

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